The present invention relates to a system for controlling the shifting of an automatic transmission of a has a "D" selected position in which all n forward gears are detected by a shifting program that determines the gear shift. An electronic control unit operates as a function of parameters of the driving state, engine operating point, and the position of the selector lever. The control unit can be actuated through the selector device when the latter is in the "D" selected position, into two shift positions optionally and pulsewise. An upshift limitation of the upshift program in one shift position, when the gear selected in the previous "D" selected position is not equal to n, decreases by one gear in steps, while in the other shift position, when the gear selected in the previous "D" selected position is not equal to 1, is expanded by one gear in steps.
In a known system of the type shown, for example, in DE 37 17 674 A1 with a selector lever guided in a shift gate, the shift gate has an L-shaped shift gate section, in which a lengthwise section with the "R" selection position runs rearward relative to the length of the vehicle from the "P" selection position located at the front, and terminates in a transverse section with the "N" selection position. Another lengthwise section runs rearward from the end of the transverse section opposite the "R" selection position and has a shift slot for the selector lever running in the lengthwise direction. In the shift slot, which is located in the transverse direction opposite the "N" selection position opposite the "R" selection position, a central spring-locking selection position "D, 1-n" is provided, in which all the forward speeds are detected by the shifting program of the control unit. In front of and behind selection position "D 1-n" there is a shift position ST, in which a step shift control can be shifted upward or downward by the selector lever. "1-n" represents the upshift limiting stages that can be controlled by the step shift control.
The purpose of this known system is to ensure that inadvertent improper shifts through the neutral position are avoided in the system for controlling the gearshift, and the movements required to actuate the selector lever resemble those of the shift lever of a manual transmission.
A system for controlling the shifting of an automatic transmission is known from U.S. Pat. No. 5,085,106 in which a selector keypad is used to actuate the selector for selected positions P-R-N-D-2-1. The selector keypad has a corresponding row of selector buttons located from top to bottom as well as laterally next to the steering wheel on the dashboard.
A system for controlling the shifting of an automatic transmission of a motor vehicle is described from EP 0 444 250 A1 in which a selector device operated by hand through a manual selector lever has a selected position "D" in which all of the n forward speeds are detected by a shifting program that determines the gearshifts. The program is located in an electronic control unit that operates as a function of the parameters of the driving state, the engine operating point, and the position of the manual selector lever. The control unit can be actuated optionally and pulsewise into two shift positions through the manual selector lever when the latter is in selected position "D". In the two shift positions, a stepwise upward or downward shift by one gear at a time is initiated from the current gear. The shift program is necessarily shut off when moving the manual selector lever from the "D" position into one of the shift positions for the stepwise shifting of the gears.
Similarly, EP 0 467 773 A1 shows a system for controlling the shifting of an automatic transmission of a motor vehicle in which a selector device actuated manually by a manual selector lever has a "D" selected position in which all four forward speeds are detected by a shifting program which determines the gearshifts in an electronic control unit that operates as a function of the parameters of the driving state, the engine operating point, and the position of the manual selector lever. The control unit can be actuated through the selector device, when the manual selector lever is in an "M" position, into two shifting positions optionally and pulsewise, in which an upshift or downshift by one gear is triggered stepwise. In this system, the manual selector lever is guided in a selector slot that extends in a straight line from front to rear in the direction of travel, at the front end of which selector slot the "P" position is located and at whose rear end the position "1" for first gear is located. While positions "R", "N", and "D" follow the "P" position in the usual sequence rearward, the "M" position is located in the selector slot immediately between the "D" position and the "1" position for first gear. The second gear and third gear are then manually shiftable by the manual selector lever in the "M" position in which the shifting program is shut off. An upper rpm limit is provided in this case for second gear, above which a shift into third gear is triggered when the engine rpm reaches its permissible maximum. Conversely, a lower rpm limit is critical for third gear, below which a shift into second gear is triggered when the engine rpm reaches a lower limiting value that causes the vehicle to stop.
In a certain known transmission of the planetary design in which the reaction drive element of first gear in coasting is supported by a freewheel to the housing, a lower rpm limit for second gear corresponds to the lower rpm limit for third gear to avoid stopping the vehicle. This is true of an upper rpm limit for first gear, above which a shift into second gear to avoid inadmissible engine rpms is triggered. As far as the upper rpm limit for second gear is concerned, however, it applies only to the range between partial and full load, since the upper rpm limit for first gear in the partial load range is displaced toward lower rpms in order to utilize the engine-braking effect, which does not exist in first gear during coasting because of the freewheel, in second gear even at low speeds.
An object of the present invention is to expand the range of functions of the electronic transmission control so that manual selection intervention in both directions is made possible, i.e. an early upshift is also possible, without thereby simultaneously having to leave the selected position "D" in the "fully automatic shifting program" mode.
This object has been achieved according to the present invention in an advantageous manner by providing that, in shift position "D(+)" for stepwise removal of the upshift limitation regardless of the shift program, an upshift can be triggered by setting a downshift limitation blocking those gears which are lower than the new gear selected by the upshift, against the shift program and an upshift or downshift limitation triggered by a shift position "D(+)" or "D(-)" by fulfillment of at least one predetermined condition such as the expiration of a delay period or the existence of a gear identity or the manner of accelerator operation or the like, is again removable automatically.
In the system according to the present invention, the shifting program remains fully automatic in the "D" selection position, and remains so. In other words, the performance of a downshift by way of the selector device does not result in blocking the previous speed until another manual upshift occurs. Instead, this upshift can still be made automatically by an electronic shifting device, in which the required conditions have been met.
The present invention can be provided both with a selector lever guided in a shift gate of the selector device, with a rocker switch for the shift positions corresponding to the known system of the type shown in DE 37 17 674 A1, and also with a selector keypad of the known arrangement in U.S. Pat. No. 5,085,106, whereby in the case of the selector keypad, for example, two shift buttons of this kind can be provided for shift positions "D (+)" and "D (-)" on both sides of the selector button for selected position "D" The system according to the present invention offers an option for adapting the shifting program to the driver's desire depending on the nature and frequency of the driver's interventions via the selector device.
An embodiment of the present invention is provided with a selector lever which effectively utilizes a parallel arrangement "H-rocker" of a second rocker switch with an "M" position and manual shifting program.
Moreover, the present invention provides, in addition to an expanded scope of function, simultaneous relief for the driver. That is, the possibility for the driver to intervene in selected position "D" in both directions without having to retract it, as well as by the possibility for shutting off the automatic function (position "M") which likewise can be performed directly through the selector device.
The expanded scope of function is obtained in the system according to the present invention from the combination of automatic shifting functions and manual intervention capability, on one hand, as well as the support of new, electronically realized shifting programs on the other hand.
In the system according to the present invention, the individual positions of the selector device have the following functions:
"P", "N", "R"--function as in an automatic transmission. PA1 "D"--the transmission operates in accordance with its shifting program; the manually operable selector element additionally functions as a shifting member and thus permits manual intervention in both directions as well. PA1 "M"--manual shifting by selector element; the automatic shifting program does not function (until an upshift at the regulation limit).
Advantageously, the present invention utilizes an alphanumeric display of the selector lever position and/or the current gear in an instrument cluster. A program selector switch can be eliminated in favor of an adaptive shifting program.
In an embodiment of the present invention with a selector lever that acts in the "D" selection position on a rocker switch or itself acts as a rocker switch, the rocker switch is provided in both "N" positions with an electrical contact as well as with a mechanical resistance which the driver can feel (i.e., pressure point). The selector lever cannot lock in these "N" positions, but automatically returns to the middle position (e.g., a return spring), but without a mechanical resistance being felt again.
Buffering of the electric contact is provided by software, as well as a protective function against inadvertent locking of the selector lever in one end position of the rocker switch, for example by resting some object thereagainst. In this case, only exactly one shift function will be performed.
Manual shifting through two or more gears can be advantageously performed by operating the selector device several times in quick succession.
The four selector positions "P", "N", "R", "D"="M" are provided in the hydraulic transmission control. In the electronic control there are at least three positions "P"="N"="R", "D", "M" and in positions "D" and "M", the two contacts of the shift positions.
Important new functions can be accomplished in the electronic transmission control by the system according to the present invention.
Following an operation of the selector in selected position "D", the full scope of functions of the automatic system is retained. Thus, for example, in the selector lever gate in known arrangements, downshifting with the selector lever, before a curve for example, initially always requires moving the selector lever to "D", since the automatic transmission otherwise cannot shift up again. In the system according to the invention, however, with appropriate driving behavior, a subsequent upshift is performed automatically. For this purpose, a state is assumed in the shifting logic when a shift is made with the selector device, in which the opposite shift according to the shift curve is initially prevented. This can only be performed as soon as the driver has conveyed his or her wishes by correspondingly changing the driving state. Therefore, the criterion for removing the shifting block can be coupled with the driver's wish (i.e., for example, at the accelerator).
In addition, the driver, by moving into the "M" position, can turn off this automatic removal of the shifting block at any time in favor of completely manual operation.
Thus, the system according to the present invention especially advantageously supports the use of a shift prevention logic which, in addition to intervention through the selector device, can also be provided for other functions in electronic transmission control (e.g., accelerator operation, frequency of shifting, and adaptation to road resistance.
Beginning with the premise that the driver does not want to operate the selector device at a precise moment and is satisfied with the existing shifting program, each selector actuation should perform an adaptation of the shifting program, with an influence in both directions by the shifting element being possible.
Such a function can logically supplement any other adaptation algorithms (e.g. adaptation to road resistance) and also offers advantages when there is an adaptive shifting program available that always assumes the same original state each time the vehicle is started. The adaptation capability through the selector device described above is helpful in this regard in order to adjust the shifting program as quickly as possible to the curve selected by the driver.
Another aspect of the present invention connects the electronic control unit with the electro-hydraulic shifting device of the transmission by a control line for gearshifts between two forward gears that are adjacent in terms of their gear ratios.
These and further objects, features and advantages of the present invention will become more readily apparent from the following detailed description thereof when taken in conjunction with the accompanying drawings of a selector lever guided in a shift gate and, more particularly, wherein: